Whole blood collected from volunteer donors for transfusion into recipients is typically separated into its components: red blood cells, white blood cells, platelets, plasma and plasma proteins, by apheresis or other known methods. Each of these blood components are typically stored individually and are used to treat a multiplicity of specific conditions and disease states. For example, the red blood cell component is used to treat anemia, the concentrated platelet component is used to control bleeding, and the plasma component is used frequently as a source of Clotting Factor VIII for the treatment of hemophilia.
After the components are separated, the white blood cell component is typically discarded, unless the cells are needed for specific applications such as photoimmune therapy or photophoresis. Cell separation procedures are not 100% effective. There is unusually some small percentage of other types of cells which are carried over into a separated blood component. Undesirable cells are typically cells of a different type which are carried over in some percentage into a desirable component. Cells such as white blood cells, which may transmit infections including HIV and CMV as well as causing other transfusion-related complications such as Transfusion-Associated Graft vs. Host Disease (TAGVHD), graft-vs-tumor responses and cytokine production are considered undesirable. The white blood cells present in the transfused blood product can also induce recipient immune responses directly by acting as antigen-presenting cells or indirectly by serving as a source of antigen that can be processed and presented by antigen-presenting cells. The recipient antidonor responses can include responses that eliminate donor cells, production of alloantiantibodies, and the induction of immunoregulatory responses that can result in increased infections, increased risk of tumor relapse, and enhanced survival of transplanted organs.
Ways to reduce the risks of these transfusion related complications from white blood cells is either to reduce the number of white blood cells transfused into a recipient, and/or to effectively destroy the viability and capacity of any transfused white blood cells to function post transfusion. White blood cells include granulocytes, monocytes and lymphocytes.
Current methods used to deplete contaminating white blood cells in blood products to be transfused include leukocyte filtration, UV irradiation of platelet concentrates and gamma irradiation of red blood cells and platelet concentrates. These methods do not completely eliminate the white blood cells however, and gamma and UV irradiation affect the cell quality of desired blood components such as platelets and red blood cells.
The blood or blood component to be transfused may also be contaminated with microorgansisms which may cause infections or unwanted immune reactions in the transfusion recipient. Microorganisms which may be present include, but are not limited to, viruses, (both extracellular and intracellular), bacteria, fungi, blood-transmitted parasites and protozoa.
Photosensitizers, or compounds which absorb light of a defined wavelength and transfer the absorbed energy to an electron acceptor may be a solution to the above problems, by inactivating pathogens contaminating a blood product without damaging the desirable components of blood. For the purposes of this invention, the general term “pathogen” may encompass any undesirable organism which may be found in blood or a blood product. Pathogens may be undesirable cells such as white blood cells, or may include microorganisms such as bacteria, parasites or viruses.
There are many pathogen reduction compounds known in the art to be useful for inactivating microorganisms or other infectious particles. Examples of such photosensitizers include porphyrins, psoralens, dyes such as neutral red, methylene blue, acridine, toluidines, flavine (acriflavine hydrochloride) and phenothiazine derivatives, coumarins, quinolones, quinones, and anthroquinones.
Dardare et al. showed in a study of the binding affinities of several common photosensitizers that both psoralen and methylene blue substantially bind to nucleic acids, phospholipid membranes and proteins in typical pathogen eradication experiments.
Although many publications have shown that damage to nucleic acids can be caused by photosensitizers and light, the issue of whether induction of damage to the nucleic acids of pathogens and undesirable cells is maintained over time, and after the pathogen reduced cells have been infused into a recipient has not been addressed.
One study done by R. Mababagloob et al. looked to see what effect S-59 and S-303 (psoralens) had on the DNA repair mechanisms of D. radiodurans, a bacteria which has multiple genomic copies and redundant repair mechanisms. The authors found that the above treatment in combination with UVA light or change in pH, resulted in 1 S-303 adduct for every 114 genomic DNA base pairs and 1 S-59 adduct for every 58 genomic DNA base pairs. However, this study did not examine whether the damage to the DNA was maintained after treatment, or was repaired by the bacteria. (Mababangloob, R., Castro, G., Stassinopoulos, A.; Helinx Technology, Utilized in the Intercept Blood System, Effectively Inactivates Deinoccus radiodurans, a Bacterium with Highly Efficienty DNA Repair; Abstract presented at the 44th Annual Meeting of the American Society of Hematology, 2002).
It is towards the method of pathogen reducing blood and blood components by inducing permanent damage to the nucleic acids of pathogens that the present invention is directed. Permanent damage means that the inactivated pathogens are unable to re-activate upon storage or upon infusion into a patient.